An image forming apparatus, such as a copying machine, a printer, a facsimile machine, a plotter, or a multifunction printer having copying, printing, scanning, and facsimile functions, can form an image on a recording medium (e.g., a sheet) by a liquid discharging method. For example, a recording head (e.g., a liquid discharging head) discharges a recording liquid (e.g. an ink drop) onto a conveyed sheet to form an image on the sheet. Alternatively, an image forming apparatus can form an image on a sheet by an electrophotographic method. A conveying roller pair feeds the sheet bearing the image to an output tray so that a user can pick up the sheet.
In an image forming apparatus using the liquid discharging method, a sheet bearing an image may slip on a conveying roller pair while the sheet is nipped and conveyed by the conveying roller pair. When an ink drop forming the image on the sheet is not dried, the conveying roller pair may scrape the image on the sheet and may stain the sheet, resulting in formation of a faulty image. The ink drop may be transferred from the sheet onto the conveying roller pair and may stain the conveying roller pair, decreasing a conveying performance of the conveying roller pair. The ink drop transferred to the conveying roller pair may be transferred back to a sheet.
To prevent a sheet from slipping on the conveying roller pair, an exemplary image forming apparatus includes an upstream conveying roller pair and a downstream conveying roller pair. The upstream conveying roller pair is disposed upstream from the downstream conveying roller pair in a sheet conveyance direction. The downstream conveying roller pair rotates at a speed smaller than a speed at which the upstream conveying roller pair rotates, so that a sheet is slacked between the upstream conveying roller pair and the downstream conveying roller pair.
To slack the sheet, guides, opposing each other to form a conveying path provided between the upstream conveying roller pair and the downstream conveying roller pair, face each other with a substantial distance therebetween. Namely, a large space is needed in the conveying path to slack the sheet between the upstream conveying roller pair and the downstream conveying roller pair. As a result, the image forming apparatus has a large size and the guides may not easily guide a foremost head of a sheet to a nip formed by each of the upstream conveying roller pair and the downstream conveying roller pair.
Even when the downstream conveying roller pair rotates at a lower speed than the upstream conveying roller pair, the downstream conveying roller pair may draw a sheet at a relatively higher speed due to change in the rotating speed of the downstream conveying roller pair. Accordingly, the slack of the sheet is decreased and thereby the sheet may easily slip on the downstream conveying roller pair.